mail_send_message

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations indicate destructiveHint=true, and the description reinforces with '[IRREVERSIBLE]'. It also states 'Requires confirm:true', which is a key safety behavior. No contradictions with annotations. However, it does not detail side effects like irreversible deletion or behavior on failure.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is very concise: one sentence with the core action, two usage modes, and a key requirement. No filler or redundant explanation. Front-loads the irreversible nature.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers the two primary usage patterns and the confirm requirement, which are the most critical aspects. It omits cc, bcc, and attachment parameters, but the schema has some descriptions for those. Given the tool's complexity (9 params, two modes), the description is adequate but could be slightly more comprehensive.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description adds meaning beyond the schema by explaining the two parameter groups (composeSessionId vs to/subject/content) and warning about fromAddress fallback behavior. The schema only describes 3 of 9 parameters, so the description compensates partially but does not cover cc, bcc, or attachmentPaths details.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description starts with '[IRREVERSIBLE] Send an email', clearly stating the action. It explains two modes (send existing draft or compose and send in one call), which distinguishes it from sibling tools like mail_create_draft and mail_delete_message.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly tells when to use each of the two modes: use composeSessionId to send a draft, or pass to/subject/content to compose and send. It also requires confirm:true, which is a critical condition. It does not mention when not to use this tool, but the modes cover the main scenarios.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.